Canal irrigation- (topics covered) Types of Impounding structures: Gravity dam – Diversion Head works - Canal drop – Cross drainage works – Canarl egulations – Canal outlets – Cana ll ining - Kennadys and Laceys Regim et heory

2. Canals
Canals artificial ( man made) channels, generally regular in shape,
Which are constructed to convey water to the farm fields from a
River or Reservoir.

3. Types of Canals-PerennialCanals
Examples: The Bhakra Canal, The Eastern Yamuna Canal, The Indira Gandhi Canal (Rajasthan)

4. gyuj
Types of Canals- Productive & Protective
Canals

5. gyuj
Types of Canals- Irrigation
Canals

6. gyuj
Types of Canals- Carrier & feeder
Canals

7. gyuj
Types of Canals- Navigation Canals

8. gyuj
Types of Canals- Power Canals

9. gyuj
Types of Canals- Unlined
Canals

10. gyuj
Types of Canals- Lined & Unlined
Canals

11. gyuj
Field Channels/water course

13. Types of Canals- Canal network

15. gyuj
Types of Canals- Ridge Canal

16. Types of Canals- Contour Canal

17. IMPOUNDING STRUCTURE
• It is an Hydraulic Structure
• Stored the water for various purpose
• Ex:
• Dam,
• Weir,
• Barrages, etc.,

18. WEIR:
• Weir is an impenetrable boundary which is
developed over a river or waterway to raise the
water level on the upstream side.
• In this system, the water level is raised up to the
required height and the excess water is permitted
to discharge over the weir.
• Weir is mainly constructed across an immersion
river or waterway.

20. BARRAGE:
• When adjustable gates are installed in a
weir to keep up the surface the water at a
diverse level at various time, is called
barrage.
• In this system, the water level is balanced
by operating the shutters or gates. The
gates are provided at different levels and
operated by cables from a cabin.
• These gates are supported on piers at both
ends. The pier to pier distance is called
bay.

21. BARRAGES ARE CONSIDERED BETTER THAN WEIRS
due to the following reasons:
• Barrages offer better control on the river outflow as well as discharge in the
offtaking canal.
• With proper regulation and with the help of undersluices and sediment
excluders, the upstream region in the vicinity of the headwork's can be kept free of
sediment deposition so that sediment-free water enters the offtaking canal.
• Because of the lower crest level of a barrage, the afflux during floods is small.
• It is possible to provide a roadway across the river at a relatively small
additional cost.

22. UNDERSLUICES
• The construction of weir across a river results in ponding up of water and causes
considerable sediment deposition just upstream of the canal head regulator. This
sediment must be flushed downstream of the weir.
• This is done by means of undersluices (also called sluice ways or scouring
sluices).
• A weir generally requires deep pockets of undersluices in front of the head
regulator of the offtaking canal, and long divide wall to separate the remaining
weir bays from the undersluices.
• The undersluices are the gate-controlled openings in continuation of the weir
with their crests at a level lower than the level of the weir crest.
• The undersluices are located on the same side as the offtaking canal. If there are
two canals each of which offtakes from one of the banks of the river, undersluices
are provided at both ends of the weir.

24. GRAVITY DAMS
A gravity dam is a solid concrete or masonry structure which ensures stability
against all applied loads by its weight alone without depending on arch or beam
action.
Such dams are usually straight in plan and approximately triangular in cross
section.
Gravity dams are usually classified with reference to their structural height which
is the difference in elevation between the top of the dam (i.e., the crown of the
roadway, or the level of the walkway if there is no roadway) and the lowest point in
the excavated foundation area,
exclusive of such features as narrow fault zones
• Gravity dams up to 100 ft (30.48 m) in height are generally considered as low dams.
• Dams of height between 100 ft (30.48 m) and 300 ft (91.44m) are designated as
• medium-height dams.
• Dams higher than 300 ft (91.44 m) are considered as high dams.

25. FORCES ON GRAVITY DAMS
1. Dead Load
2. Reservoir and Tail-water
Loads
3. Uplift Forces
4. Silt Load
5. Ice Pressure
6. Wave Pressure
7. Earthquake
8. Other Miscellaneous
Loads

26. CAUSES OF FAILURE OF A GRAVITY DAM
A gravity dam may fail on account of overturning.
For a gravity dam to be safe against overturning,
The dimensions of the dam should be such that the resultant of all the forces
intersects the base of the dam within its middle-third portion. Consider any
horizontal section (including the base) of a gravity dam and the resultant of all the
forces acting on the dam above the section.
A gravity dam is considered safe against overturning if the
criteria of:
(i) no tension on the upstream face,
(ii) adequate resistance against sliding, and
(iii) suitable quality and sufficient strength of concrete/masonry of dam and its foundation
are
satisfied.

27. RIVER TRAINING FOR CANAL HEADWORKS
I. To prevent outflanking of the structure,
II. To minimise possible cross-flow through the barrage or weir which may endanger
the structure and protection works.
III. To prevent flooding of the riverine lands upstream of the barrages and weirs, and
IV. To provide favourable curvature of flow at the head regulator from the
consideration of entry of sediment into the canal.
The following types of river training structures are usually provided for weirs:
I. Guide banks,
II. Approach embankments,
III. Afflux embankments, and
IV. Groynes or spurs.

29. Alignment of Canals
 Water-shed Canal
 Contour Canal
 Side-slope Canal

30. Water-shed canal

31. Contour canal

32. Side-slope canal
SIDE SLOPE
CHANNEL
1000
950 900
GROUND CONTOURS
Fig:Alignment of a side slope canal

33. Distribution system for Canal Irrigation
BARRAGE OR
WEIRSILT EXCLUDER
CANAL HEAD
REGULATOR
SEDIMENT ESCAPE
CHANNEL
MAIN CANAL
BRANCH CANAL Q > 30 m3/s
MINOR
Q < 2.5 m3/s
DISTRIBUTARY
Q < 30 m3/s
WATER COURSE
(Field Channel)
OUTLET
FIELD
Main Canal Branch
Canal Distributaries
Minors
Water-courses
RIVER

34. CROSS DRAINAGE WORKS
A cross drainage work is a
structure carrying the discharge
from a natural stream across a
canal intercepting the stream.
Canal comes across obstructions
like rivers, natural drains and other
canals.
The various types of structures
that are built to carry the canal
water across the above
mentioned obstructions or vice
versa are called cross drainage
works

35. TYPES
It is generally a very costly item and should be avoided by:
• Diverting one stream into another.
• Changing the alignment of the canal so that it crosses below the junction of two
streams.
the structures that fall under this type are:
Cross Section of Aqueduct
• An Aqueduct
• Siphon Aqueduct

36. AQUEDUCT:
When the HFL of the drain is sufficiently below the bottom of the canal such that the
drainage water flows freely under gravity, the structure is known as Aqueduct.
• In this, canal water is carried across the drainage in a trough supported on piers.
• Bridge carrying water
• Provided when sufficient level difference is available between the canal and natural
and canal bed is sufficiently higher than HFL.

37. SIPHON AQUEDUCT:
In case of the siphon Aqueduct, the HFL of the drain is much higher above the canal bed,
and water runs under siphonic action through the Aqueduct barrels.
The drain bed is generally depressed and provided with pucci floors, on the upstream side,
the drainage bed may be joined to the pucca floor either by a vertical drop or by glacis of
3:1. The downstream rising slope should not be steeper than 5:1. When the canal is
passed over the drain, the canal remains open for inspection throughout and the damage
caused by flood is rare. However during heavy floods, the foundations are susceptible to
scour or the waterway of drain may get choked due to debris, tress etc.
The structures that fall under this type are:
1. Super passage
2. Canal siphon or called syphon only

38. 1. SUPER PASSAGE:
The hydraulic structure in which the drainage is passing over the irrigation canal is
known as super passage. This structure is suitable when the bed level of drainage is
above the flood surface level of the canal. The water of the canal passes clearly
below the drainage
A super passage is similar to an aqueduct, except in this case the drain is over the
canal.
The FSL of the canal is lower than the underside of the trough carrying drainage water.
Thus, the canal water runs under the gravity.
Reverse of an aqueduct

39. 2. CANAL SYPHON:
If two canals cross each other and one of the canals is siphoned
under the other, then the hydraulic structure at crossing is called
“canal siphon”. For example, lower Jhelum canal is siphoned
under the Rasul-Qadirabad (Punjab, Pakistan) link canal and
the crossing structure is called “L.J.C siphon”
In case of Siphon Super Passagesiphon the FSL of the canal is
much above the bed level of the drainage trough, so that the
canal runs under the siphonic action.
The canal bed is lowered and a ramp is provided at the exit so that
the trouble of silting is minimized.
Reverse of an aqueduct siphon
In the above two types, the inspection road cannot be provided
along the canal and a separate bridge is required for roadway.
For economy, the canal may be flumed but the drainage trough
is never flumed.

40. CLASSIFICATION OF AQUEDUCT AND SIPHON AQUEDUCT
Depending upon the nature of the sides of the aqueduct or siphon aqueduct - classified
Type I:
• Sides of the aqueduct in earthen banks with complete earthen slopes. The length of
culvert should be sufficient to accommodate both, water section of canal, as well as
earthen banks of canal with aqueduct slope. Sides of the aqueduct in earthen banks,
with other slopes supported by masonry wall. In this case, canal continues in its
earthen section over the drainage but the outer slopes of the canal banks are
replaced by retaining wall, reducing the length of drainage culvert.
Type II:
• Sides of the aqueduct made of concrete or masonry. Its earthen section of the canal
is discontinued and canal water is carried in masonry or concrete trough, canal is
generally flumed in this section.

41. CANAL LINING
Canal lining is the process of reducing seepage loss of irrigation water by adding an
impermeable layer to the edges of the trench. Seepage can result in losses of 30 to
50 percent of irrigation water from canals, so adding lining can make irrigation
systems more efficient.

42. TYPES OF CANAL LINING
There are varieties of linings that are available today but we will be discussing the
following three:
1. Plain Cement Concrete Lining
2. Reinforced Cement Concrete Lining
3. Brick Lining

43. 1. PLAIN CEMENT CONCRETE LINING
This lining is recommended for the canal in full banking. The cement concrete lining is widely
accepted. It can resist the effect of scouring and erosion very efficiently. The velocity of flow
may be kept above 2.5 m/s. It can eliminate completely growth of weeds. The lining is done
by the following steps:
(a) Preparation of sub-grade
The sub grade is prepared by ramming the surface properly with a layer of sand (about 15
cm). Then slurry of cement and sand (1:3) is spread uniformly over the prepared bed.
(b) Laying of concrete
The cement concrete of grade M15 is spread uniformly according to the desired thickness,
(generally the thickness varies from 100mm to 150 mm). After laying, the concrete is tapped
gently until the slurry comes on the top. The curing is done for two weeks. As the concrete
is liable to get damaged by the change of temperature, the expansion joints are provided at
appropriate places.

44. 2. BRICK LINING
This lining is prepared by the double layer brick flat soling laid with cement mortar (1:6)
over the compacted sub-grade. The first class bricks should be recommended for
the work. The surface of the lining is finished with cement plaster (1:3). The curing
should be done perfectly.
This lining is always preferred for the following reasons:
• This lining is economical.
• Work can be done very quickly.
• Expansion joints are not required.
• Repair works can be done easily.
Bricks can be manufactured from the excavated earth near the site. However this lining
has certain disadvantages:
• It is not completely impervious.
• It has low resistance against erosion.
• It is not so much durable.

45. 3. REINFORCED CEMENT CONCRETE LINING
Sometimes reinforcement is required to increase the resistance against cracks and
shrinkage cracks.
The reduction in the cracks results in less seepage losses.
However this reinforcement does not increase the structural strength of the lining.
This reinforcement adds 10 to 15 percent to the cost and for this reason steel
reinforcement is usually omitted except for very particular situations.

46. CANAL REGULATION STRUCTURES
canal obtains its share of water from the pool behind a barrage through a structure called
the canal head regulator. Though this is also a regulation structure for controlling the
amount of water passing into the canal (with the help of adjustable gates), it shall be
discussed under diversion works
These structures may be described as follows:
1. Drops and falls to lower the water level of the canal
2. Cross regulators to head up water in the parent channel to divert some of it through an
off take channel, like a distributary.
3. Distributary head regulator to control the amount of water flowing in to off take channel.
4. Escapes, to allow release of excess water from the canal system

48. 1. CANAL DROPS AND FALLS
A canal has a designed longitudinal
slope but has to pass through an
undulating terrain. When a canal
crosses an area that has a larger
natural surface slope, a canal
drop, also called fall in India, has
to be provided suitably at certain
intervals

49. FALLS OF ANTIQUITY
The Ogee type of fall has been one of the first to be tried in the Indian canal irrigation system,
probably since more than a century back
The crest of the fall was in the same elevation as that of the upstream section of the canal.
This caused a sharp draw-down of the water surface on the upstream side. On the downstream,
the drop in elevation added energy to the falling water which exited the falls as a shooting
flow, causing erosion of the canal bed immediately downstream.

50. The rapid-fall was tried in some of the north-Indian canals which were constructed with
boulders cemented together by lime concrete (Figure). These were quite effective
but, the cost being prohibitive, was gradually phased out.

51. The trapezoidal-notch fall consists of one or more notches in a high crested wall across
the channel with a smooth entrance and a flat circular lip projecting downstream
from each notch to disperse water (Figure 5). This type of fall was started around the
late nineteenth century and continued to be constructed due to its property of being
able to maintain a constant depth-discharge relationship, until simpler and economical
alternatives were designed.

52. 3. CANAL REGULATORS & DISTRIBUTARY HEAD REGULATOR
These include the cross regulator and the
distributary head regulator structures for
controlling the flow through a parent canal and
its off-taking distributary as shown in Figure 1.
They also help to maintain the water level in
the canal on the upstream of the regulator.
Canal regulators, which are gated
structures, may be combined with bridges
and falls for economic and other
considerations, like topography, etc.
A typical view of a distributary head regulator
and a cross regulator (shown Figure)

53. 4. CANAL ESCAPES
These are structures meant to release excess
water from a canal, which could be main
canal, branch canal, distributary, minors etc.
Though usually an irrigation system suffers
from deficit supply in later years of its life,
situations that might suddenly lead to
accumulation of excess water in a certain
reach of a canal network may occur due to the
following reasons:
• Wrong operation of head works in trying to
regulate flow in a long channel resulting in
release of excess water than the total demand
in the canal system downstream.
• Excessive rainfall in the command area
leading to reduced demand and
consequent closure of downstream gates.
• Sudden closure of control gates due to a canal
bank breach.

54. CANAL OUTLET
• Canal outlets, also called farm turnouts in some countries, are structures at the
head of a water course or field channel
• Various types of canal outlets have been evolved from time to time but none has
been accepted as universally suitable.
• It is very difficult to achieve a perfect design fulfilling both the properties of ‘flexibility’
as well as ‘sensitivity’ because of various indeterminate conditions both in the
supply channel and the watercourse of the following factors: •
• Discharge and silt •
• Capacity factor •
• Rotation of channels •
• Regime condition of distribution channels, etc.

55. TYPES
These modules are classified in three types, which are as follows:
(a) Non-modular outlets These outlets operate in such a way that the flow passing
through them is a function of the difference in water levels of the distributing channel
and the watercourse. Hence, a variation in either affects the discharge. These outlets
consist of regulator or circular openings and pavement. The effect of downstream water
level is more with short pavement.
(b) Semi-modular outlets The discharge through these outlets depend on the water level
of the distributing channel but is independent of the water level in the watercourse so
long as the minimum working head required for their working is available.
(c) Module outlets The discharge through modular outlets is independent of the water
levels in the distributing channel and the watercourse, within reasonable working limits.
This type of outlets may or may not be equipped with moving parts. Though modular
outlets, like the Gibb’s module, have been designed and implemented earlier, they are
not very common in the present Indian irrigation engineering scenario.

56. Design Parameters
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Cross sectional Area (A)
Depth of water over the bed
Slope of the bed (S)
Rugosity Co-efficient (N)
Hyd Mean Depth ( R)
Velocity of Flow (V)
(D)
Non-Silting Velocity/Non
Discharge (Q)
Silt Factor (f)
B/D ratio
Scouring Velocity / Critical Velocity (Vo)

57. Kennedy’s Theory
1.
2.
Based on the Upper Bari Doab Canal System
Flowing water experiences friction against the canal bed which causes
surface
These eddies are responsible to keep the silt in suspension
Hence the bed width is proportional to the silt supporting power
Critical Velocity Vo= 0.55mD0.64
eddies on the
3.
4.
5.
5. Critical Velocity Ratio m= critical velocity for the area/ critical velocity of UBD canal
Type of Silt Critical Velocity Ratio (m)
Light sandy silt ( northern India) 1.0
Coarser light sandy silt 1.10
Sandly loamy silt 1.2
Hard soil 1.3
Indus river 0.7

58. Kennedy’s Theory
7. Mean velocity of flow is given by Kutter’s formula:
V=C*√RS
where

59. Kennedy’s Theory-Design Steps
Case 1: Q, N, m and S are known
Step1: Assume a value of D
Step 2: Calculate Vo from Vo= 0.55mD0.64
Step 3: Find A from A=Q/Vo
Step 4: Knowing D and A Find bed width B for a trapezoidal channel ( side slope is ½:1)
A= BD+ (D2/2)
Step 5: Calculate Perimeter and hydraulic mean depth
P=B+D√5 R=A/P
R=(BD+ (D2/2) /(B+D√5)
Step 6: Calculate the mean velocity by Kutter’s equation
V= √RS
If the value of V=Vo, the assumed depth is correct, if not repeat the calculations by changing D till the
velocities are same

60. Kennedy’s Theory-Design
Case 2: Q, N, m and B/D=x ratio are known
Steps
Find Discharge Q= A*Vo = 0.55m(x+0.5)D2.64
Step1: Calculate A in terms of D, A= BD+ (D2/2) = D2 (x+0.5)
Step 2: We know that Vo= 0.55mD0.64
D= (Q/ (0.55m(x+0.5))(1/2.64)
Step 3: Calculate Vo from Vo= 0.55mD0.64
Step 4: Calculate the Slope S by Kutter’s equation by trial & error
V= √RS

61. Kennedy’s Theory-Problem
DESIGN AN IRRIGATION CHANNEL ON KENNEDY’S THEORY, TO
CARRY A DISCHARGE OF 40 CUMECS. TAKE N=0.0225 AND
m=1.05. THE CHANNEL HAS A BED SLOPE OF 1IN 5000

62. Kennedy’s Theory-Problem
Given:
Q=45 cumecs, N=0.025, m=1.05
Solution:
Step1: Assume a value of D =2 m
Step 2: Vo from Vo= 0.55mD0.64 = 0.9m/s
Step 3: Find A from A=Q/Vo = 50sqm
Step 4: Knowing D and A Find bed width B for a trapezoidal channel ( side slope is ½:1)
A= BD+ (D2/2) , B=24m
Step 5: Calculate Perimeter and hydraulic mean depth
P=B+D√5 =28.47m R=A/P
R=(BD+ (D2/2) /(B+D√5), =1.756m
Step 6: Calculate the mean velocity by Kutter’s equation
V= √RS = 0.926 m/s
V>VO ( INCREASE THE VALUE OF D & TRY AGAIN)

63. Kennedy’s Theory-Problem
Given:
Q=45 cumecs, N=0.025, m=1.05
Solution:
Step1: Assume a value of D =2 .2m
Step 2: Vo from Vo= 0.55mD0.64 = 0.957m/s
Step 3: Find A from A=Q/Vo = 47.04sqm
Step 4: Knowing D and A Find bed width B for a trapezoidal channel ( side slope is ½:1)
A= BD+ (D2/2) , B=20.28m
Step 5: Calculate Perimeter and hydraulic mean depth
P=B+D√5 =25.2m R=A/P
R=(BD+ (D2/2) /(B+D√5), =1.867m
Step 6: Calculate the mean velocity by Kutter’s equation
V= √RS = 0.965 m/s
V= VO Hence the assumed D is correct. For further precision, D can be assumed as 2.23m

64. Kennedy’s Theory-Problem
DESIGN AN IRRIGATION CHANNEL TO CARRY A DISCHARGE OF
14 CUMECS. ASSUME N=0.0225, M=1 AND B/D=5.7

65. Kennedy’s Theory-Design
GIVEN
Q=14cumecs, N=0.0225, m=1 and B/D=5.7
Solution:
Steps
Find Discharge Q= A*Vo = 0.55m(x+0.5)D2.64
Step1: Calculate A in terms of D, A= BD+ (D2/2) = D2 (x+0.5), A=6.2D2
Step 2: We know that Vo= 0.55mD0.64
D= (Q/ (0.55m(x+0.5))(1/2.64) =1.71m
Step 3: Calculate Vo from Vo= 0.55mD0.64 = 0.775m/s
Step 4: Calculate the Slope S by Kutter’s equation by trial & error by V=Vo
V= √RS
S= 1/5100

66. Lacey’s RegimeTheory
1.
2.
Based on the Upper Bari Doab Canal System
Flowing water experiences friction against the canal bed which causes
surface
These eddies are responsible to keep the silt in suspension
Hence the bed width is proportional to the silt supporting power
Critical Velocity Vo= 0.55mD0.64
eddies on the
3.
4.
5.
5. Critical Velocity Ratio m= critical velocity for the area/ critical velocity of UBD canal
Type of Silt Critical Velocity Ratio (m)
Light sandy silt ( northern India) 1.0
Coarser light sandy silt 1.10
Sandly loamy silt 1.2
Hard soil 1.3
Indus river 0.7

67. Lacey’s Regime Theory
REGIME CHANNEL: